Transporting ethane in a crude oil pipeline



Oct. 3, 1967 R. E. STYRING ETAL 3,344,583

TRANSPORTING ETHNE IN A CRUDE OIL PIPELINE Filed Dec.

INVENTORS RALPH E. sTYRING HENRY E DUN LA P CHARLES L. ROGERS BY Oct. 3, 1967 R E. STYRING ETAL 3,344,583

TRANsPoRTING ETHANE IN A CRUDE OIL PIPELINE 2 Sheets-Sheet 2 Filed Dec. 9, 1964 m .n 2238 mmmnzww @F3255 w .Sl

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LNA m, .mak M m w W ,n m@ :IIITJ B United StatesY Patent 3,344,583 TRANSPORTING ETHANE IN A CRUDE OIL PIPELINE Ralph E. Styring, Henry F. Dunlap, and Charles L. Rogers, Dallas, Tex., assignors to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Penn- Sylvania Filed Dec. 9, 1964, Ser. No. 417,087 19 Claims. (Cl. 55-44) This invention pertains to methods for mixing ethane with crude oil to form a liquid solution, for transporting this liquid solution in a pipeline at standard operating temperatures, Vand for extracting from the solution the ethane thus transported.

Previously, it has been proposed to transport butane, propane, natural gasoline and condensate in crude oil pipelines by blending small percentages by volume of these light hydrocarbons with crude oil. It has also been proposed to remove these light hydrocarbons at the reiinery by distillation. But when ethane has been transported in pipelines of any substantial length, it has always been thought necessary to pump the ethane in a gaseous state. In addition, whenever it was necessary to ship large quantities of relatively pure ethane by means other than pipelines, it has always been thought necessary to ship the ethane in insulated, refrigerated containers. Such methods of shipping ethane have many disadvantages.

Accordingly, it is an object of this invention to provide a better, safer and more economical method for transporting ethane over long distances.

Another object of this invention is to provide a method for transporting in a long pipeline large quantities of ethane in liquid solution with crude oil.

Still other objects of this invention are to provide methods for blending ethane and crude oil to form a liquid solution, for transporting the mixture in a liquid state in a long pipeline, and for recovering the ethane thus transported.

rThese and other objects of this invention are more speciiically illustrated and described by reference to the following description and accompanying drawings which schematically depict the various embodiments ofV this invention and in which:

FIGURE 1 is a block diagram representing an ethane and crude oil blending system connected to a long pipeline transporting system which is in turn connected to an ethane recovery system. s

FIGURE 2 shows a system similar to that of FIGURE 1 wherein ethane is separated from methane using gasoline or hexane as the absorbent, the ethane is compressed and blended with crude oil, and ethane recovery from a crude oil-ethane mixture is accomplished by a series of iiash separators, compression of the overhead flashed vapors and reabsorption of heavier hydrocarbons in the crude oil.

FIGURE 3 shows the blending system of FIGURE 2 using crude oil as the absorbent for ethane.

FIGURE 4 shows a recovery system using a single distillation column.

FIGURE 5 shows a recovery system using a steam stripper and a distillation column in series.

It has been found that ethane may be efficiently, economically and safelyV transported in solution with crude oil if the vapor pressure of the solution is maintained at a level bellow 400 pounds per square inch absolute at 95 F. and if there is at .least 3 percent by volume of ethane in the solution. In addition, it has also been found that the solution must be owed through a pipeline for a substantial distance. When two or more pump stations are spaced along the pipeline to iiow the liquid, the pressure 3,344,583 Patented Oct. 3, 1967 on the solution in the pipeline between pumping stations is maintained at a level above the bubble point of the solution. The pressure on the solution may drop below the bubble point between the last pump station and the point where the ethane is to be separated from the solution. Moreover, it has been found that the presence of propane and butane in the solution must be less than l5 percent by liquid volume. Methane may be present provided that the above conditions are met.

Accordingly, as illustrated in FIGURE 1, this invention comprises, blending at first point 11 in a pipeline, crude oil with a hydrocarbon comprised of at least 10 percent by volume of ethane to form a solution or mixture of the crude oil and ethane. As previously pointed out, it is important that the nal mixture contains less than 15 percent by liquid volume of propane and butane, at least 3 percent -by liquid volume of ethane and have a final vapor pressure of less than 400 pounds per square inch absolute at 95 F. The blended mixture is then flowed through pipeline 13 for a substantial distance to second point 15 on the pipeline. Preferably this distance will be at least 20 miles. The solution mixture is flowed through the pipeline by pump or booster stations 17. On long lines two or more pump stations will be used, 4and it is important that at all times during the liow of the blended crude oil-ethane solution between pump stations, the pressure on the mixture be above the bubble point of the mixture. At a third point between the` last pump station and second point 15 the pressure of the solution may be allowed to drop below the bubble point because at second point 15 the ethane Iwill be separated. But generally, it is preferred to maintain the pressure of the mixture above the bubble point between the lirst and second points. As stated, lthis pressure is maintained by spacing pump or booster stations 17 along the line at intervals which maintain this pressure in an economical manner. On long lines, such intervals will be approximately 25 to 75 miles. As stated, during all but the last stage of transport of the solution mixture, the solution is always in the liquid state thereby eliminating the many problems that would be encountered if the ethane were allowed to form bubbles or vaporize. At second point 15 on the pipeline, the ethane is extracted from the solution so as to separate and recover at least 85 percent by liquid volume of the ethane added to the crude oil.

Ethane may be added to or blended with the crude oil in a number of ways. For example, if substantially pure ethane were available, it could be bled directly in the crude oil in the pipeline, but generally the ethane will be mixed with methane and two ways of handling such a mixture and blending ethane in crude oil are illustrated in FIG- URES 2 and 3. In the system shown in FIGURE 2, a

hydrocarbon gaseous mixture containing at least 25 percent by volume of ethane is introduced into fractionating absorber 19 through inlet line 21 at a first intermediate point between the top and bottom of the fractionating absorber. Simultaneously, with introduction of the mixture, there is introduced through return line 23 at a point between the top of fractionating absorber 19 and the rst intermediate point, hexane or gasoline to absorb hydrocarbons containing at least two carbon atoms from the iirst hydrocarbon gaseous mixture. At first overhead point 25 above the point of introduction of the hexane or gasoline, there is removed a iirst vapor phase containing at least percent by volume of methane. The liquid remaining in the fractionating absorber is withdrawn from a point below the lirst intermediate point through stripper inlet line 27. When desired, heat may be added to the fractionating absorber by way of side heater 29. The liquid from the fractionating absorber is introduced into stripping column 31 at a second intermediate point between the top and bottom of the stripping column. At second overhead point 33, which is above the second intermediate polnt at which the liquid from the absorber is introduced into the stripper, there is removed a second vapor phase enriched in ethane. The top pressure and temperature of the stripping column are maintained at the dew point of the second vapor phase and the bottom temperature and pressure of the stripping column are maintained at the bubble point of the liquid in the bottom of the stripping column. Heat is added to the stripping column by way of side heater 35. The liquid remaining in the stripping column is withdrawn from the stripping column at a point below the second intermediate point by way of return line 23. This liquid is returned through pump 37 to the absorber. The second vapor phase removed from the stripping column at second overhead point 33 is compressed by cornpressor 39 to a pressure greater than the bubble point of the crude oil-ethane mixture, for example, 1200 p.s.i. The compressed second vapor phase is then blended in blender 41 with crude oil flowing in pipeline 43 so as to form a mixture of crude oil and compressed, liquefied second vapor phase. This mixture contains at least 3 percent by volume of ethane and will contain less than that amount of ethane which would raise the vapor pressure of the mixture to 400 pounds per square inch absolute at 95 F. The crude oil is at a pressure above the bubble point of the compressed, liquefied second vapor phase during the blending of the two streams. The pressure of the crude oil is maintained by pump 45. The blended crude oil-ethane mixture is then `flowed through pipeline 13 to the point of ethane extractionas previously mentioned.

In the system shown in FIGURE 3, crude oil is used as the absorbing liquid rather than gasoline. In this system, a portion of the crude oil fiowing in crude oil line 47 is withdrawn and pumped by way of pump 49 through crude oil inlet line 51 into fractionating absorber 19 at a point between the top of the absorber and the intermediate point wherein the first hydrocarbon gaseous mixture is introduced. The crude oil absorbs hydrocarbons containing at least two carbon atoms from the first hydrocarbon gaseous mixture. At overhead point 25, above the point of introduction of the crude oil, there is removed a vapor phase containing at least 85 percent by volume of methane. At a point below the first intermediate point of introduction of the hydrocarbon gaseous mixture through outline line 53, there is Withdrawn liquid crude oil enriched in ethane. This liquid is passed through pump 55 where the pressure of the liquid is increased to a predetermined pressure above the bubble point of the enriched mixture. This enriched crude oil is then blended with high pressure crude oil fiowing in pipeline 57 to form a mixture containing at least 3 percent by volume of ethane and less than the amount of ethane required to raise the vapor pressure of the mixture to 400 pounds per square inch absolute at 95 F. The pressure of the crude oil in pipeline 57 is maintained by pump 59.

Refer now to the different systems for recovering or extracting ethane from crude oil as shown in FIGURES 2, 4, and 5. These methods are all suitable for recovering ethane from a mixture of ethane and crude oil containing less than l percent by liquid volume of propane and butane. The mixture is herein called a crude oil-ethane mixture and contains at least 3 percent by liquid volume of ethane and has a vapor pressure of less than 400 pounds per square inch absolute at 95 F.

The simplest method of extracting ethane from this mixture is shown in FIGURE 4 wherein the mixture is introduced through inlet line 61 into distillation column 63 at a point intermediate the top and bottom of the distillation column. Distillation column 63 is maintained at a top temperature and pressure which are at the dew point of the overhead vapor from the distillation column and at a bottom temperature and pressure which are at the bubble point of the liquid in the distillation column. Heat is added to the distillation column by way of side heater 65. Under these conditions, there is separated at overhead point 67 a vapor phase enriched in ethane. This vapor phase is cooled at condenser 69 to form a gas phase enriched in and comprised substantially of ethane and a liquid phase enriched in and comprised substantially of hydrocarbons having more than two carbon atoms. The cooled vapors and liquids are passed to separator 71 wherein the liquid phase is recycled into the distillation column by introducing the liquid phase at a point between the intermediate point wherein the crude oil-ethane mixture was introduced into the distillation column and the overhead point where the vapors are withdrawn. At the top of separator 71, the ethane is recovered by way of line 73. The liquid remaining in the distillation column is withdrawn at a point below the intermediate point by way of line 75. This liquid remainder is comprised essentially of crude oil containing less than 15 percent by liquid volume of propane and butane.

A Ibetter method of recovering or extracting the ethane from the crude oil-ethane mixture is shown in FIGURE 5. In this method, the mixture flowing in line 61 is passed through heater 77 where the crude oil-ethane mixture is heated to a temperature of at least 300 F. The heated mixture is introduced into steam stripper 79 at a first point intermediate the top and bottom of the steam stripper to separate at first overhead point 81 a first vapor phase enriched in ethane. Simultaneously with introduction of the heated mixture, steam from steam line 83 is introduced into the stripper at a point between the first intermediate point and the bottom of the steam stripper. This steam is at a pressure at least as great as the pressure inside steam stripper 79. The first vapor phase removed from the steam stripper at first overhead point 81 is cooled at cooler 8S to form a first gas phase enriched r in ethane and a first liquid phase enriched in hydrocarbons having more than two car-bon atoms and a liquid water phase. This cooled first vapor phase is passed to separator 87 where the liquid water phase is separated and removed. The first liquid hydrocarbon phase is also separated and recycled into the steam stripper by introducing this first liquid hydrocarbon phase at a point between the first intermediate point and the first overhead point. The first gas phase is also separated at separator 87. This first gas phase is then introduced into distillation column 89 by way of line 91 at a second point intermediate the top and bottom of distillation column 89. At second overhead point 93, there is separated a second vapor phase enriched in ethane. This is accomplished by maintaining the top temperature and pressure of distillation column 89 at the dew point of the second vapor phase and by maintaining the bottom temperature and pressure of the distillation column at the bubble point of the liquid therein. Heat may be added to the column by way of distillation column side heater 95. The second vapor phase removed at second overhead point 93 is cooled at condenser 97 to form a second gas phase enriched in and comprised substantially of ethane and a second liquid phase enriched and comprised substantially of hydrocarbons having more than two carbon atoms. This cooled second vapor phase is passed to separator 99 wherein the second liquid phase is separated and recycled into the distillation column by introducing the second liquid phase at a point between the second intermediate point and the second overhead point on said distillation column. The second gas phase from separator 99 is the recovered ethane which is recovered in line 101. The liquids remaining in the steam stripper 79 and in distillation column 89 are withdrawn through line 103 from points on the steam stripper and distillation column which are below the first and second intermediate points. This liquid remainder is comprised substantially of the crude oil containing less than l5 per cent by volume of propane and butane.

A third and preferred system for extracting ethane from the crude oil-ethane mixture is shown in FIGURE 2.

In this system, crude oil in pipeline 13 is introduced into first flash separator 105 at a first intermediate point between the top and bottom thereof. The top pressure in lirst flash separator 105 is at least 50 p.s.i. below the vapor pressure of the mixture at the operating temperature of the llash separator. A lirst vapor phase enriched in ethane is removed at first overhead point 107. The liquid remaining in the first flash separator is withdrawn at a point below the first intermediate point and is introduced by way of Iline 109 into second flash separator 111 at a second intermediate point between the top and bottom of the second ilash separator. A second vapor phase enriched in ethane is removed at a second overhead point 113. The top pressure in the secondY flash separator is between 20 p.s.i. and 100 p.s.i. less than the pressure in the first flash separator. The liquid remaining in the second Hash separator is Withdrawn at a point below the second intermediate point on the second llash separator. This liquid is introduced by way of line 115 into third flash separator 117 at a third intermediate point between the top and bottom thereof. The top pressure in the third flash separator is between 20 p.s.i. and 100 p.s.i. less than the pressure in the second ilash separator. A third vapor phase enriched in ethane is removed at third overhead point 119. The liquid remaining in the third flash separator is withdrawn at a point below the third intermediate point and is introduced by way of line 121 into fourth flash separator 123 at a fourth intermediate point between the top and bottom thereof. As shown in FIG- URE 2, fourth ilash separator 123 is the last separator in the series. The last flash separator in the series must operate at a subatmospheric pressure between 0 and 6 p.s.i. absolute. A fourth overhead Vapor phase enriched in ethane is removed at fourth overhead point 125.

Each of the overhead vapor phases from each of the flash separators are individually compressed to `a predetermined pressure by Way of compressors 1,27 and each of the compressed vapor phases are cooled at coolers 129. The cooled, compressed vapor phases from all but the lirst flash separator are passed to over-head separators 131 to divide the cooled, compressed vapor phases into a liquid phase and a gas phase. The gas phases from these overhead separators are each combined with the overhead vapor phase from the llash separator preceding it in the series before the overhead vapor phases `are compressed. The liquid phase from the overhead separator for the flash separator operating `at subatmospheric pressure will Ibe essentially crude oil and is returned rby way of pump 133 and line 135 to the crude oil recovery portion of the system hereinafter described. The other liquid phases separated at the other overhead separators are combined through pumps 137 and line 139 with the cooled, compressed vapor phase from the compressor for the overhead vapor phase from the lirst flash separator.

The Icombined liquids and compressed vapors are introduced by way of line 141 into fractionating absorber 143 at a point intermediate the top and bottom of the absorber. The liquid remaining in the last flash separator of the series, or the fourth separator of FIGURE 2, is withdrawn by way of line 145. At least a portion of this liquid is increased in pressure by pump 147 to a predetermined pressure and is introduced by way of line 149 into fractionating absorber 143 at a point between the intermediate point of introduction of the combined liquids and compressed overhead vapor phases at the top of the absorber. The predetermined pressures for the liquid from the ash separator and for the combined, compressed vapor phases is at least as great as the top pressure of the absorber. At the top of the absorber through line 151 is withdrawn a vapor `phase comprised of at least 75 percent by volume of ethane. The temperature in the absorber is maintained by side heater 153. At a point below the intermediate point of Vintr-oduction of the combined liquids and compressed overhead vapor phases, the

liquid remaining in the absorber is withdrawn through crude oil recovery line 155. Part of the liquid remaining in the last flash separator of the series may be added directly to oil recovery line 155 by Way of pump 157. The liquid in line 155 is comprised essentially of the crude oil containing less than 15 percent by volume of propane and butane.

In the ethane recovery system shown in FIGURE 2. there are four flash separators. The minimum number of llash separators is three for an ethane recovery system when the ethane has been mixed with crude oil containing less than 15 percent by liquid volume of propane and butane, but four flash separators are shown since this is the preferred number. Also, it should be noted that each of the flash separators must operate at a pressure between 20 p.s.i. and 100 p.s.i. less than the pressure in the ash separator just preceding it in the series. The last flash separator operates at subatmospheric pressure between 0 and 6 p.s.i. absolute regardless of the operating pressure of the flash separator just preceding the last llash separator.

In the foregoing description, there has been described a method for transporting ethane in solution with crude oil over long distances. By operating in the manner set forth, substantial economies are effected as compared to other ethane transporting systems. The description of the over-all method is followed by a description of two systems for adding ethane to crude oil. The system using crude oil as the absorbent for ethane is especially novel and useful in the over-all process. The description of the two systems for adding ethane to crude oil is followed by a description of three methods for recovering or extracting ethane from crude oil. The method using llash separators is particularly novel and useful to the over-al1 process. In this system, light ends including ethane are flashed from the crude oil-ethane mixture. The flashed light ends are compressed and the light ends heavier than ethane are then reabsorbed in the crude oil.

It will be understood that various changes in the details and arrangement of equipment which have been described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention, as expressed in the appended claims.

We claim:

1. A method for transporting ethane over substantial distances comprising separating ethane from methane to form a hydrocarbon comprised of at least 10 percent by volume of the separated ethane, blending at a first point in a pipeline, said hydrocarbon with crude oil to form a mixture of saidV crude oil and said hydrocarbon, said mixture containing less than l5 percent by liquid volume of propane and butane and containing at least 3 percent by liquid volume of ethane and having a vapor pressure of less than 400 pounds per square inch absolute at 95 F., flowing said mixture through said pipeline for a substantial distance to a second point on said pipeline, and separating from said mixture at said second point at least percent by volume of said ethane in said hydrocarbon blended with said crude oil.

2. The method of claim 1 wherein the distance between the first and'second points is at least 20 miles.

3. The method of claim 1 wherein the pressure of the mixture in the pipeline is maintained by at least two pumping stations spaced along said pipeline and the pressure of said mixture in said pipeline between said pumping stations is maintained at a level above the bubble point of said mixture.

(b) simultaneously introducing at a point between said top of said absorber and said first intermediate point an absorbent selected from the group consisting of hexane and gasoline to absorb hydrocarbons containing at least two carbon atoms from said first hydrocarbon,

(c) removing at a first overhead point above the point of introduction of said absorbent a first vapor phase containing at least 85 percent by volume of methane,

(d) withdrawing the liquid remaining in said absorber from a point below said first intermediate point,

(e) introducing said liquid from said absorber into a stripping column at a second intermediate point between the top and bottom of said stripping column,

(f) removing at a second overhead point above said second intermediate point a second vapor phase enriched in ethane,

(g) maintaining said stripping column at a top pressure and temperature which are at the dew point of said second vapor and at a bottom temperature and pressure which are at the bubble point of the liquid in said stripping column,

(h) withdrawing the liquid remaining in said stripping column from a point below said second intermediate point and introducing said liquid from said stripping column into said absorber at said point between said top of said absorber and said tirst intermediate point,

(i) compressing said second vapor phase to a pressure at least as great as the bubble point of said crude oilethane mixture,

(j) blending said compressed liquefied second vapor phase with crude oil flowing in a pipeline to form said crude oil-ethane mixture comprised of a mixture of said crude oil and said compressed liquefied second vapor phase, Said mixture containing at least 3 percent by volume of ethane and having a vapor pressure of less than 400 pounds per square inch absolute at 95 F.,

(k) owing said mixture through said pipeline to a second point on said pipeline, and

(l) separating from said mixture at said second point at least 85 percent by volume of said ethane in said mixture.

5. The method of claim 4 wherein the distance between the first and second points is at least 20 miles.

6. The method of claim 4 wherein the pressure of the mixture in the pipeline is maintained by at least two pumping stations spaced along said pipeline and the pressure of said mixture in said pipeline between said pumping stations is maintained at a level above the bubble point of said mixture.

7. A method for transporting ethane over long substantial distances comprising:

(a) introducing at an intermediate point between the top and bottom of a fractionating absorber a first hydrocarbon containing at least 25 percent by volume yof ethane,

(b) simultaneously introducing at a point between said top of said absorber and said intermediate point crude oil to absorb hydrocarbons containing at least two `carbon atoms from said first hydrocarbon,

(c) removing at an overhead point above the point of introduction of said crude oil a vapor phase containing at least 85 percent by volume of methane,

(d) withdrawing from said absorber at a point below said first intermediate point liquid crude oil enriched in ethane,

(e) increasing the pressure of said enriched crude oil from said absorber,

(f) blending said enriched crude oil with crude oil flowing in a crude oil pipeline to form a mixture, said mixture containing at least 3 percent by volume of said ethane and having a vapor pressure of less than 400 pounds per square inch absolute at 95 F.,

(g) flowing said mixture through lsaid pipeline for 'a substantial distance to a second point on said pipeline, and

(h) separating from said mixture at said second point at least 95 percent by volume of said ethane in said mixture.

8. The method of claim 7 wherein the distance between the first and second points is at least 20 miles.

9. The method of claim 7 wherein the pressure of the mixture in the pipeline is maintained by at least two pumping stations spaced along said pipeline and the pressure of said mixture in said pipeline between said pumping stations is maintained at a level above the bubble point of said mixture.

10. A method of adding ethane to crude oil comprising:

(a) introducing at an intermediate point between the top and bottom of a fractionating absorber la first hydrocarbon containing at least 25 percent by volume of ethane,

(b) simultaneously introducing at a point between said top of said absorber and said intermediate point crude oil to labsorb hydrocarbons containing at least two carbon atoms from said first hydrocarbon,

(c) removing at an overhead point above the point of introduction yof said crude oil a vapor phase containing at least percent by volume of methane,

(d) withdrawing from said absorber at a point below said first intermediate point liquid crude oil enriched in ethane,

(e) increasing the pressure of said enriched crude oil from said absorber, and

(f) blending said enriched crude oil with crude oil flowing in a crude oil pipeline to form a mixture, said mixture containing at least 3 percent by volume of said ethane and having a vapor pressure of less than 400 pounds per square inch absolute at F.

11. A method for transporting ethane over long distances comprising:

(a) separating ethane from methane to form a hydrocarbon comprised of at least 10 percent by volume of the separated ethane,

(b) blending lat a lirst point in a pipeline said hydrocarbon with crude oil to form a liquid mixture of said crude oil and said hydrocarbon, said liquid mixture containing less than 15 percent by -liquid volume of propane and butane and containing at least 3 percent by liquid volume of ethane and having a vapor pressure of less than 400 pounds per square inch absolute at 95 F.

(c) flowing said liquid mixture through said pipeline for a substantial distance to a second point on said pipeline,

(d) introducing said liquid mixture at a point intermediate the top and bottom of a distillation column, said distillation column being maintained at a top temperature and pressure which are at the dew point of the overhead vapor from said distillation column and at a bottom temperature and pressure which are at the bubble point of the liquid in said distillation column, to separate at an overhead point a vapor phase enriched in said ethane,

(e) cooling said vapor phase from said distillation column to form a gas phase enriched in and comprised substantially of said ethane and a liquid phase enriched in and comprised substantially of hydrocarbons having more than two carbon atoms,

(f) separating said liquid phase from said gas phase and recycling said liquid phase into said distillation column by introducing said liquid phase into said distillation column at a point between said intermediate point and said overhead point, and

(g) withdrawing the liquid remaining in said distillation `column from a point below said intermediate point, said liquid remainder being comprised essentially of said crude oil.

12. The method of claim 11 wherein the vdistance between the first and second points is at least 20 rniles.

13. The method of claim 11 wherein the pressure of the mixture in the pipeline is maintained by at least two pumping stations spaced along said pipeline and the pressure of said mixture in said pipeline between said pumping stations is maintained at a level above the bubble point of said mixture.

14. A method for transporting ethane over long distances comprising:

(a) separating ethane from methane to form a hydrocarbon comprised of at least percent by volume of the separated ethane,

(b) blending at a irst point in a pipeline said hydrocarbon with crude oil to form a liquid mixture of said crude oil and said hydrocarbon, said liquid mixture containing less than 15 percent by liquid volume of propane and butane and containing at least 3 percent by liquid volume of ethane and having a vapor pressure of less than 400 pounds per square inch absolute at 95 F.,

(c) iiowing said liquid mixture through said pipeline for a substantial distance to a second point on said pipeline,

(d) heating said liquid mixture to a temperature of at least 300 F., l

(e) introducing said heated mixture into a steam stripper at a first point intermediate the top and bottom of said steam stripper to separate at a iirst overhead point a rst vapor phase enriched in said ethane,

(t) simultaneously introducing steam into said steam stripper at a point between said first intermediate pointy and said bottom of said steam stripper, said steam being at a pressure at least as great as the pressure inside said steam stripper,

(g) cooling said tirst vapor phase from said iirst overhead point of said steam stripper to form a iirst gas phase enriched in said ethane, a rst liquid hydrocarbon phase enriched in hydrocarbons having more than two carbon atoms and a liquid water phase,

(h) separating and removing said liquid water phase,

(i) separating and recycling said first liquid hydrocarbon phase by introducing said first liquid hydrocarbon phase into said steam stripper at a point between ,said rst intermediate point and said first overhead point,

(j) separating and introducing said first gas phase into a distillation column at a second point intermediate the top and bottom of said distillation column to separate at a second overhead point a second vapor phase enriched in said ethane, said distillation column being maintained at a top temperature and pressure which are at the dew point of said second vapor phase and at a bottom temperature and pressure which are at the bubble point of the liquid in said distillation column, i

(k) cooling said second vapor phase from said ldistlllation column to form a second gas phase enriched in and comprised substantially of said ethane and a second liquid phase enriched in and comprised substantially of hydrocarbons having more than two carbon atoms,

(l) separating and recycling said second liquid phase into said distillation column by introducing said second liquid phase into said distillation column at a point between said second intermediate point and said second overhead point, and

(m) withdrawing the liquid remaining in said steam stripper and in said distillation column from a point below said iirst and second intermediate points, said liquid remainder being comprised substantially of said crude oil.

15. The method of claim 14 wherein the distance between the irst and second points is at least miles.

10 16. The method of claim 14 wherein the pressure of the liquid mixture in the pipeline is maintained by at least two pumping stations spaced along said pipeline and the pressure of said liquid mixture in said pipeline between said pumping stations is maintained at a level above the bubble point of said mixture.

17. A method for transporting ethane over long distances comprising:

(a) separating ethane from methane to form a hydrocarbon comprised of at least 10 percent by volume of the separated ethane,

(b) blending at a first point in a pipeline said hydrocarbon with crude oil to form a liquid mixture of said crude oil and said hydrocarbon, said liquid mixture containing less than l5 percent by liquid volume of propane and butane and containing at least 3 percent by liquid volume of ethane and having a vapor pressure of less than 400 pounds per square inch absolute at F.,

(c) flowing said liquid mixture through said pipeline for a substantial distance to a second point on said pipeline,

(d) introducing said liquid mixture into a rst ash separator at a first intermediate point between the top and bottom of said irst flash separator, said iirst liash separator having a top pressure at least 50 p.s.i. below the vapor pressure of said mixture at the operating temperature of said ash separator,

(e) withdrawing the liquid remaining in said first flash separator at a point below said first intermediate point and introducing said liquid from said irst ilash separator into a second llash separator at a second intermediate point between the top and bottom of said second ilash separator to remove at a second overhead point a second vapor phase enriched in said ethane, the top pressure in said second flash separator being between 20 p.s.i. and 10() p.s.i. less than the pressure in said first flash separator,

(t) withdrawing the liquid remaining in said second flash separator at a point below said second intermediate point and repeating step (d) for at least one additional ash separator with the last flash separator operating at a subatmospheric pressure between 0 and 6 p.s.i. absolute,

(g) withdrawing each of said overhead vapor phases from each of said lash separators and individually compressing each of said overhead vapor phases to a predetermined pressure,

(h) combining said individually compressed overhead vapor phases and introducing said combined cornpressed vapor phases into a fractionating absorber at a point intermediate the top and bottom of said absorber,

(i) withdrawing the liquid remaining in said last ash separator,

(j) increasing the pressure of at least a part of said liquid from said last ilash separator to a predetermined pressure,

(k) introducing said liquid from said last ash separator at said increased pressure into said fractionating absorber at a point between the intermediate point of introduction of said combined compressed overhead vapor phases and the top of said 4absorber,

(l) said predetermined pressures for said liquid from said last ash separator and said combined compressed vapor phases being at least as great as said top pressure of said absorber,

(m) withdrawing at the top of said absorber a vapor phase comprised of at least 75 percent by volume of said ethane, and

(n) withdrawing at a point below said intermediate 11 point of introduction of said combined compressed overhead vapor phases the liquid remaining in said absorber, said liquid remainder being comprised essentially of said crude oil. 18. The method of claim 17 wherein the distance between the rst and second points is at least 20 miles. 19. The method of claim 17 wherein the pressure of the liquid mixture in the pipeline is maintained by at least two pumping stations spaced along said pipeline and the pressure of said liquid mixture in said pipeline between said pumping stations is maintained at a level above the bubble point of said mixture.

1 2 References Cited UNITED STATES PATENTS 6/1930 Scharpenberg 48-190 5/1941 Robinson et al 55-40 12/ 1953 Gilmore 55-40 12/1960 Hasche 48-l90 lO/1965 Byerly et al. 208-356 2/1966 Secord et al. 48-190 10 SAMIH N. ZAHARNA, Primary Examiner.

REUBEN FRIEDMAN, Examiner. C. HART, Assistant Examiner. 

1. A METHOD FOR TRANSPORTING ETHANE OVER SUBSTANTIAL DISTANCES COMPRISING SEPARATING ETHANE FROM METHANE TO FORM A HYDROCARBON COMPRISED OF AT LEAST 10 PERCENT BY VOLUME OF THE SEPARATED ETHANE, BLENDING AT A FIRST POINT IN A PIPELINE, SAID HYDROGEN WITH CRUDE OIL TO FORM A MIXTURE OF SAID CRUDE OIL AND SAID HYDROCARBON, SAID MIXTURE CONTAINING LESS THAN 15 PERCENT BY LIQUID VOLUME OF PROPANE AND BUTANE AND CONTAINING AT LEAST 3 PERCENT BY LIQUID VOLUME OF ETHANE AND HAVING A VAPOR PRESSURE OF LESS THAN 400 POUNDS PER SQUARE INCH ABSOLUTE AT 95* F., FLOWING SAID MIXTURE THROUGH SAID PIPELINE FOR A SUB- 